import java.io.*;
import java.util.*;

class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader bu=new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb=new StringBuilder();
        int n=Integer.parseInt(bu.readLine());
        String s[]=bu.readLine().split(" ");
        int a[]=new int[n],i;
        for(i=0;i<n;i++) a[i]=Integer.parseInt(s[i]);

        long p[]=new long[n+1],M=(int)1e9+7;
        p[0]=1;
        for(i=1;i<=n;i++) p[i]=p[i-1]*3%M;

        long ans=0,psum=1,cur;
        for(i=0;i<n;i++)
        {
            cur=psum*a[i]%M;
            //System.out.print(cur+" "+(p[n-2-i]*2%M)+" ");
            if(i!=n-1) cur=cur*p[n-2-i]%M*2%M;
            ans=(ans+cur)%M;
            //System.out.println(cur);
            psum=psum*a[i]%M;
        }
        System.out.println(ans);
    }
}